I think that part of it might be that unless you are immune compromised, you simply cannot have a "systemic" yeast infection. This is a good summary of the systemic candida hypothesis and the criticisms against it: http://www.quackwatch.org/01QuackeryRel ... ndida.html
Even Andrew Weil
says that it's impossible.
There is little hard evidence for these ideas. Diagnoses of systemic candidiasis usually have no scientific basis, and most of the recommended treatments for it waste time and money. Anyone with yeast growing in the blood or vital organs would be critically ill in an intensive care unit. Despite this medical reality, systemic candidiasis remains a popular diagnosis in some segments of the alternative medicine community. My belief is that its persistence is an example of our fears of foreign invaders; it satisfies a need to blame our maladies on an external cause.
If your gut is unhappy after a course of antibiotics, it will not take a lifetime of probiotics to restore your gut to normal.